沙棘绕实蝇的生物学习性

[目的]沙棘绕实蝇严重危害沙棘果实,使沙棘种植地蒙受巨大经济损失。研究其生物学习性,可以为有效监测和控制沙棘绕实蝇提供理论指导。[方法]通过室内人工饲养和野外观察,研究沙棘绕实蝇的羽化、交尾、产卵、化蛹等生物学习性和野外发生动态。[结果]沙棘绕实蝇成虫在野外从6月中旬至8月上旬均可见到,发生量受天气影响较大;成虫主要集中在6:00—10:00羽化,羽化量占当日羽化量的81.3%,羽化高峰出现在8:00—9:00;化蛹时间主要集中在凌晨0:00—6:00,尤其是3:00—6:00钻出果实化蛹的幼虫数量较多,与其它时间段有明显差异;交尾时间主要集中在白天光照比较强的时间段,一天当中有两次交尾高峰,分别出现在12:00—13:00和16:00—17:00,交尾平均持续时长为239±11.86 min;沙棘绕实蝇产卵期沙棘果长径6.65±0.28 mm,宽径5.47±0.40 mm,一果只产一卵。[结论]沙棘绕实蝇在内蒙古磴口地区一年发生一代,幼虫钻蛀果实,蛹隐藏在地下,成虫期较短,防治工作应集中在成虫期进行。     

Fumigant and repellent activities of essential oil from <Emphasis Type="Italic">Coriandrum sativum</Emphasis> (L.) (Apiaceae) against red flour beetle <Emphasis Type="Italic">Tribolium castaneum</Emphasis> (Herbst) (Coleoptera: Tenebrionidae)

The biological activity of essential oil extracted from coriander, Coriandrum sativum L. (Apiaceae) against eggs, larvae and adults of Tribolium castaneum (Herbst) was investigated in a series of laboratory experiments. Bioassays conducted in air-tight glass chambers showed vapour toxicity and strong repellency on filter paper arena test towards all the stages used. Responses varied significantly (P < 0.001) within insect stages, dosages and exposures. At 12.0 μg/ml dosage, mortality of adults reached 95%, but for 12-, 14- and 16-days larvae, mortalities were 65, 74 and 82%, respectively. On the developmental inhibition, individuals fumigated at the larval stage confirmed that the percentage of larvae reaching to pupal stage and pupae to adult stage, decreased significantly (P < 0.001) with increasing dosage concentration. The oil fumigation yielded 100% mortality for T. castaneum larvae, pupae and adults at 0.08 μg/ml dosage. The oil had fumigant activity against eggs and the toxicity progressively increased with increased exposure times and concentrations. One hundred per cent T. castaneum egg mortalities were obtained with oil fumigation at 20 μg/ml and 96 h exposure period. C. sativum oil also showed highly repellent activity to the adults of T. castaneum, with overall repellency was 90% and at a dosage of 12 μg/ml repellency was 100% in a filter-paper arena test.     

Aphidicidal activity of some indigenous plant extracts against bean aphid <Emphasis Type="Italic">Aphis </Emphasis><Emphasis Type="Italic">craccivora</Emphasis> Koch (Homoptera: Aphididae)

Aphidicidal activity of hot and cold water extracts of some indigenous plants, Azadirachta indica A. Juss (neem), Calotropis procera (Aiton) W.T. Aiton (akanda), Polygonum hydropiper L. (biskatali) and Ipomoea sepiaria J. Koenig ex Roxb. (bankalmi), were tested against the bean aphid, Aphis craccivora Koch. Hot water extract of P. hydropiper and A. indica was found to be the most effective (87.6–94.5 and 80.47–89.6% mortality respectively, P < 0.01) among all the extracts. Other hot and cold water extracts also appeared to be useful (59.5–87.5% mortality) as pesticides for A. craccivora. The highest yield (3.25 kg per plant) was obtained using hot water extract of P. hydropiper followed by hot water extract of A. indica (3.15 kg per plant). The lowest yield (0.32 kg per plant) was recorded from the control block. All the phytoproduct treatments had significantly (P < 0.01) better yield than the control block.     

Potential of the entomopathogenic nematodes Steinernema feltiae , S. weiseri and Heterorhabditis bacteriophora for the biological control of the sugar beet weevil Bothynoderes punctiventris (Coleoptera: Curculionidae)

The sugar beet weevil, Bothynoderes punctiventris Germ. (Coleoptera: Curculionidae), is one of the most damaging pests of sugar beets in Turkey and has been traditionally controlled by application of large amounts of insecticides. The current study used laboratory microcosms to evaluate the possibility of using entomopathogenic nematodes as an alternative control method. The nematodes Steinernema feltiae (strain TUR-S3), Steinernema weiseri (BEY) and Heterorhabditis bacteriophora (TUR-H2) had previously been isolated from Turkey. Nematode-induced mortality generally increased as soil temperature increased from 15 to 25°C but decreased when larvae were located deeper in soil. Heterorhabditis bacteriophora caused the highest larval mortality at 25°C at all depths (5–20 cm). Steinernema feltiae and S. weiseri were more effective than H. bacteriophora at 15°C at all depths. Increasing the application rate of infective nematode dauer juveniles (DJs) affected the number of DJs that penetrated each insect larva and the number of DJs produced per insect. The highest production of DJs per larva occurred at application rates of 50 DJs/larva for S. feltiae and S. weiseri and 100 DJs/larva for H. bacteriophora. Reproduction decreased again at higher application rates. Heterorhabditis bacteriophora had the highest reproductive capability. The results indicate that S. feltiae and S. weiseri might be more effective against this pest early in the growing season when soil temperature is low and that H. bacteriophora might be more effective later in the season when temperature increases.     

Effect of ivermectin on larval mortality and reproductive potential of <Emphasis Type="Italic">Albizia</Emphasis> foliage feeder, <Emphasis Type="Italic">Spirama retorta</Emphasis> Cramer (Lepidoptera: Noctuidae)

Toxicity of ivermectin (Ivecop-12), a derivative of avermectin B, produced by a soil actinomycete, Streptomyces avermitilis, was evaluated in laboratory against the larvae of Spirama retorta Cramer (Lepidoptera: Noctuidae), a major stenophagous insect defoliator of Albizia spp. (family Leguminosae) in nurseries and young plantations. The study was conducted with eight treatment concentrations of lethal and sub-lethal doses. Results revealed that ivermectin is highly toxic and induce larval mortality when applied separately on host plant leaves and larvae, and on leaves and larvae of the insect pest together. The nature of treatment affects the larval mortality. Treatment of host plant leaves alone as well as leaves together with larvae showed 100% mortality by the treatment of 0.075% concentration whereas only 95% larval mortality was recorded due to larval treatment by the concentration of 1.2%. The LC₅₀ value of the tested product was worked out to be 0.014, 0.170 and 0.012% for leaf and larval treatments separately and leaf and larval treatments together, respectively, against the insect pest. This clearly shows that ivermectin is more effective in larval killing when ingested through food. Further, the adults developed from treatments of sub-lethal concentrations and subsequently, when mated laid significantly (P < 0.05–0.01) less number of eggs and also showed significant (P < 0.05–0.01) reduction in hatching percentage compared to control. These observations suggest that the tested bioproduct, ivermectin, interfere physiological programming of larvae thereby causing alteration in fecundity and fertility of the target insect pest.     

Wirkungen von Precocen I aufCulex quinquefasciatus Say (Diptera,Culicidae)

Zusammenfassung Es wurden die Wirkungen von Precocen I (PI) unter Laborverhältnissen auf die frühen L4 und Puppen vonCulex quinquefasciatus bei Konzentrationen von 0,001–10,0 ppm untersucht. Das Spektrum der PI-Wirkungen schloß die Larven-und Adulten-Mortalität bei 0,1–10,0 ppm ein. Die Verpuppungs-und Adultenschlüpf-Periode wurden bei Dosen von 0,001–5,0 ppm verzögert. Auf die larvalen Nachkommen vonC. qu. wirkte sich die PI-Behandlung (0,001–10,0 ppm) in verringerter Fekundität und Eischlüpfquote, verzögerte Larvenentwicklung und schließlichem Absterben aus.

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Effects of precocene I onCulex quinquefasciatus Say (Diptera, Culicidae)

The effects of precocene-I (PI) onCulex quinquefasciatus Say were studied under laboratory conditions by treating laboratory reared early 4th instar larvae and pupae with 0.001–10.0 ppm of PI. The range of PI effects included larval and adult mortalities at 0.1–10.0 ppm. Pupation and adult emergence periods were delayed at 0.001–5.0 ppm. Effects of PI were maintained to offsprings ofC. quinquefasciatus. These effects involved reduced fecundity, reduced egg hatchability and delayed larval offspring development and finally the death at 0.001–10.0 ppm of PI.

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Mit einer Abbildung und 4 Tabellen     

Maintaining <Emphasis Type="Italic">Bactrocera oleae</Emphasis> (Gmelin.) (Diptera: Tephritidae) colony on its natural host in the laboratory

The olive fruit fly, Bactrocera oleae (Gmelin.) (Diptera:Tephritidae) is a pest on olives (Olea europea) in the Mediterranean basin. An olive fruit fly colony was maintained on olives at 24 ± 1°C, 60% RH, and 16:8 h (light:dark) photoperiod with fluorescent lighting. We investigated oviposition behavior, developmental duration and weights of the biological stages, and adult longevity. A single female laid an average of 19 eggs/day and 200–350 eggs in her lifetime. The maximum number of oviposition stings in a single olive was 156.0 ± 5.77, and 28.00 ± 3.62 larvae out of it completed their development, all pupated, and all emergence successfully. Although the development period was similar for larvae and pupae, adult longevity varied. Male and female emergence percentages ranged as 38.7–52.8, and 32–39.9%, respectively. The results are presented in relation to published studies on olive fruit fly rearing.     

Development,life history characteristics and behaviour of mealybug predator, <Emphasis Type="Italic">Spalgis epius</Emphasis> (Westwood) (Lepidoptera: Lycaenidae) on <Emphasis Type="Italic">Planococcus citri</Emphasis> (Risso) (Homoptera: Pseudococcidae)

The development of immature stages, life history and behaviour of mealybug predator, Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) reared on mealybugs, Planococcus citri (Risso) (Homoptera: Pseudococcidae) was studied in the laboratory. Larvae of S. epius are a potential predator of different species of mealybugs in India. The predator completed its life cycle in 23.8 days with four larval instars. Mean incubation period of egg was 3.9 days. Mean duration of development of larval stages, prepupa and pupa was 9.4, 0.9 and 9.5 days, respectively. The first and last instar larvae measured 1.9 and 11.4 mm in length, respectively. Length and width were not significantly correlated in larvae. Head capsule width was not significantly correlated with larval length in any instar. The female-to-male sex ratio was 1.45:1. Adults were ready for mating one day after eclosion. The pairs remained in copula on an average of 61.3 min. The gravid female contained 74.6 eggs in the ovaries. Unfed butterflies (both males and females) lived 3–4 days, significantly shorter than those with access to water (6–7 days). The results of this study will be useful to utilize the predator as a biocontrol agent.     

Effect of Lecanicillium muscarium on Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae), a parasitoid of Bemisia tabaci (Hemiptera: Aleyrodidae)

Pathogenicity of Lecanicillium muscarium, against Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae), was investigated under laboratory conditions to determine if the fungal infection of the whitefly host can effect the survival, longevity and fecundity of female parasitoid. The results indicated that the number of parasitized larvae surviving a L. muscarium treatment after 6 days of oviposition decreased with increasing concentrations of L. muscarium and in later stages of development (12 days post oviposition) were not affected by fungal application. There were no significant differences on adult parasitoid survivorship after 7 days among all treatments. Maximum survivorship (73.33%) was observed for control and it was minimum (60%) at 1 × 10⁸ conidia/ml. L. muscarium showed a non significant effect on longevity and next offsprings of female parasitoids. The percentage emergence of parasitoids from the whitefly nymphs produced by the females emerged from treated pupae was almost similar. Maximum emergence (69.77%) was observed at 1 × 10⁶ conidia/ml and it was lowest (61.02%) at conidial concentration of 1 × 10⁸ conidia/ml. Maximum longevity of adult Eretmocerus sp. emerging from whitefly nymphs when treated after 12 days of postoviposition was observed for 1 × 10⁵ conidia/ml having a mean value of 5 days whereas the lowest longevity was 4.9 days observed at 1 × 10⁸ conidia/ml. The results mentioned above indicate that the interaction among biocontrol agents is positive to a greater extent with minimum risk hazards.     

Host instar suitability of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Genn.) (Hom.: Aleyrodidae) for the parasitoid <Emphasis Type="Italic">Eretmocerus mundus</Emphasis> (Hym.: Aphelinidae)

Efficient use of parasitoids in pest control depend on the knowledge of the biological relationships between host and parasitoid. Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one the most important natural enemies of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) that is found in fields and greenhouses in Adana, Turkey. Although more studies have been done to determine the relationships between E. mundus and B. tabaci, the differences among strains of E. mundus could have important biological concequences. In this study, biological characteristics of native population of E. mundus parasitization of B. tabaci (Q biotype) were determined using bean plants Phaseolus vulgaris (L.) at a constant temperature of 25 ± 1°C, relative humidity 70 ± 10% and 16:8 (L:D) photoperiod regimen. All B. tabaci nymphal instars were parasitized by E. mundus, but the mean number of daily-parasitized nymphs was highest in the second instars (15.3). In addition, second instar females had the shortest mean development time (15.2 days). Mean development times of parasitoids obtained from first, second, third and fourth B. tabaci instars varied from 15.2 to 16.2 days and 15.2 to 15.9 days for female and male, respectively. Proportion of female (♀/♂+♀) varied from first (0.53) to second (0.34) host instars. Impact of results on potential biological control of B. tabaci was discussed through conservation native natural enemies.     

银杏大蚕蛾的生物学和防治技术研究

银杏大蚕蛾在湖北一年发生一代。幼虫5龄;4、5龄幼虫有绿色型和黑色型。幼虫取食38种植物,天敌有53种。本文还叙述了该虫发生与环境的关系。防治试验表明:喷洒2.5％溴氰菊酯5000倍液、2×10~8孢子/ml白僵菌液、25％苏脲一号500倍液、1×10~8PIB/mlDjNPV虫尸液效果均很好。     

Hyptis suaveolens and Hyptis spicigera (Lamiaceae) essential oils: qualitative analysis, contact toxicity and repellent activity against Sitophilus granarius (L.) (Coleoptera: Dryophthoridae)

Essential oils from Hyptis suaveolens (L.) Poiteau (Lamiaceae) and Hyptis spicigera Lamarck (Lamiaceae) were first analysed by gas chromatography and by gas chromatography/electron impact mass spectroscopy and then evaluated for toxicity and repellent activity against Sitophilus granarius (L.) (Coleoptera: Dryophthoridae), one of the most serious worldwide stored grain pests. Fifty-six compounds have been identified in the essential oil of H. suaveolens: monoterpene hydrocarbons were the most represented volatiles (64.1%), followed by sesquiterpene hydrocarbons (24.0%), oxygenated monoterpenes (8.1%) and oxygenated sesquiterpenes (2.4%). Diterpenes and non-terpene derivatives were scarcely represented. Sixty compounds have been identified in the essential oil of H. spicigera: monoterpene hydrocarbons were the most represented class of volatiles (70.4%), followed by sesquiterpene hydrocarbons (22.6%). Results from topical applications on insects showed that both essential oils had an effective insecticidal activity. The complete kill of S. granarius was observed 24 h after treatment at a minimum effective dose of 0.4 and 0.6 μl per insect with H. suaveolens and H. spicigera oil, respectively. Results from repellency tests showed that the two essential oils had a repellent activity on S. granarius adults: at the lowest dose (2 × 10⁻⁴ μl oil per cm²), H. spicigera essential oil exhibited a higher repellent effect in comparison to H. suaveolens. No significant differences were observed for the repellent effect between the two essential oils at the highest dose (2 × 10⁻² μl oil per cm²).     

Influence of slope position, stand type and rhododendron (Rhododendron ponticum) on litter decomposition rates of Oriental beech (Fagus orientalis Lipsky.) and spruce [Picea orientalis (L.) Link]

Oriental beech (Fagus orientalis Lipsky.) and Oriental spruce [Picea orientalis (L.) Link] are the two most common tree species in northeast Turkey. Their distribution, stand type and understorey species are known to be influenced by topographical landforms. However, little information is available as to how these changes affect litter decomposition rates of these two species. Here, we investigated the effects of slope positions (top 1,800 m, middle 1,500 m and bottom 1,200 m), stand type (pure and mixed stands) and purple-flowered rhododendron (Rhododendron ponticum) on litter decomposition rates of Oriental beech and spruce for 4 years using the litterbag technique in the field. Among these three factors, stand type had the strongest influence on litter decomposition (P < 0.001, F = 58.8), followed by rhododendron (P < 0.001, F = 46.8) and slope position (P < 0.05, F = 11.6). Litter decomposition was highest under mixed beech/spruce forest, followed by pure beech and spruce forest. Beech and spruce litter decomposed much faster in mixed bags (beech–spruce) than they did separately under each stand type. Purple-flowered rhododendron significantly reduced litter decomposition of Oriental beech and spruce. Beech and spruce litter decomposed much slower at top slope position than at either bottom or middle position. Differential litter decomposition of Oriental beech and spruce was mainly due to adverse conditions in spruce forest and the presence of rhododendron on the ground which was associated with lower soil pH. Higher elevations (top slope position) slowed down litter decomposition by changing environmental conditions, most probably by decreasing temperature as also other factors are different (pH, precipitation) and no detailed investigations were made to differentiate these factors. The adverse conditions for litter decomposition in spruce forest can be effectively counteracted by admixture of beech to spruce monoculture and by using the clear-cutting method for controlling rhododendron.     

A laboratory study on the activity of <Emphasis Type="Italic">Steinernema feltiae</Emphasis> (Rhabditida: Steinernematidae) Rioja strain against horticultural insect pests

The potential of the entomopathogenic nematode Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) Rioja strain was assessed under laboratory conditions. Last instar larvae of Leptinotarsa decemlineata Say (Coleptera: Chrysomelidae), Spodoptera littoralis Boisdouval (Lepidoptera: Noctuidae) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae) were exposed to infective juveniles (IJs) under laboratory conditions. Larval mortality, days to larval death, infection cycle length, and reproductive potential were recorded. Efficacy was assessed performing dose–response experiments. The results indicate that control of L. decemlineata with S. feltiae Rioja strain is not economically profitable (LC₅₀ = 99.61 IJs/cm²), whereas results obtained for T. ni (LC₅₀ = 0.27 IJs/cm²) are promising. Due to the life cycle of this insect, the efficacy needs to be investigated in foliar application studies. The effects on S. littoralis (LC₅₀ = 0.69 IJs/cm²) was considered the most suitable for development of the Rioja strain as a biocontrol agent for soil application.     

Influence of synthetic plant growth substances on the survivorship and developmental parameters of <Emphasis Type="Italic">Spilarctia obliqua</Emphasis> Walker (Lepidoptera: Arctiidae)

The nontarget effects of three plant growth stimulants (gibberellic acid, Siapton and triacontanol) and two plant growth retardants (chlormequat chloride and mepiquat chloride) on the survivorship and developmental parameters of Spilarctia obliqua Walker (Lepidoptera: Arctiidae) were studied. For each compound, various concentrations (0.125×, 0.25×, 0.5×, × , 2× and 4×; × = labeled dose) bracketing the labeled dose were prepared by serial dilution and mixed with an artificial diet for the insect. Gibberellic acid caused an increase in the larval period at × − 4×, but no marked difference was observed in the pupal period or in larval survival at any concentration. Siapton induced a significant increase in larval period at the two highest doses but caused significant reduction in pest survival at × − 4×. Interestingly, triacontanol induced a significant reduction in pest survivorship at almost all doses. The LC₅₀ for triacontanol was 0.206% and LT₅₀ was 266.5 hours at the labeled dose. However, triacontanol did not cause any significant difference in larval or pupal periods at any dose tested. Chlormequat chloride and mepiquat chloride caused significant reduction of larval survivorship at concentrations higher than the labeled doses, and no effect on the larval period. Intriguingly, a significant reduction in pupal period was observed with chlormequat chloride at × and 0.25×. Based on the marked effect of triacontanol on pest survivorship, this study suggests incorporating triacontanol in integrated pest management modules for S. obliqua. Caution in the use of gibberellic acid and Siapton for pest infestations is also indicated.     

Acaricidal,repellent and oviposition deterrent activities of <Emphasis Type="Italic">Datura stramonium</Emphasis> L. against adult <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Koch)

The ethanol extracts obtained from both leaf and seed in the Thorn apple (Datura stramonium L.) (Solanaceae) were investigated for acaricidal, repellent and oviposition deterrent properties against adult two-spotted spider mites (Tetranychus urticae Koch) (Acari: Tetranychidae) under laboratory conditions. Leaf and seed extracts, which were applied in 167,250 and 145,750 mg/l concentrations, respectively (using a Petri leaf disc-spray tower method), caused 98 and 25% mortality among spider mite adults after 48 h. The simple logistic regression analysis showed that the independent variable, an increase in the dose of leaf extract was associated with a significant increase in the death rate of T. urticae females, but an increase in the dosage of seed extracts did not have a significant effect. Using probit analysis and estimating the parameters with a confidence limit of 95%, we determined the LC₅₀ values of leaf extract to be 70,593 mg/l. According to Pearson’s χ² test, mites showed the strongest run off to bean leaf surfaces sprayed with both leaf and seed extracts (in sub-lethal doses: <7,500 mg/l and <25,000 mg/l, respectively) and moved towards surfaces that had not been sprayed with extracts. Furthermore, repeated measures ANOVA indicated a significant difference between the number of eggs laid on unsprayed bean leaves compared to bean leaves that were sprayed with leaf and seed extracts at sub-lethal doses, 2,500 and 25,000 mg/l concentrations, respectively. These results suggest that D. stramonium extracts could be used to manage the two-spotted spider mite.     

Neem-based integrated approaches for the management of tea mosquito bug, <Emphasis Type="Italic">Helopeltis theivora</Emphasis> Waterhouse (Miridae: Heteroptera) in tea

Despite continuous use of synthetic insecticides during last two decades, the tea mosquito bug, Helopeltis theivora Waterhouse (Miridae: Heteroptera), has become the most destructive sucking pest of tea in North East India. In order to reduce the load of the synthetic chemicals in tea vis-à-vis their deleterious effect, integration of biopesticide, synthetic pesticides along with effective spraying strategies, have been attempted. The anti-insect property of “neem”, Azadirachta indica A. Juss. (Meliaceae), has been used to solve many pest problems. In this study, different azadirachtin concentrations were evaluated at different doses against the H. theivora to find out their controlling efficacy. At 50,000 ppm azadirachtin concentration 65% control of infestation could be attained, whereas at 3,000 and 10,000 ppm, gave 30–43% reduction and 300 and 1,500 ppm <30% control was possible. Further in case of 3,000 and 10,000 ppm, azadirachtin concentration 30–43% reduction was registered. Therefore, azadirachtin concentration and its dilutions are the major criteria for getting desired bioactivity. Treatments with combined formulations viz. “neem + endosulfan” or “neem + deltamethrin” recorded significant reduction in H. theivora incidence even at reduced doses, as compared to sole application of neem or synthetic insecticide at recommended doses. Effective combinations and dose of the insecticides along with their formulations in controlling H. theivora have been presented and discussed.     

Electroantennogram responses of Dendrolimus superans (Lepidoptera: Lasiocampidae) to six volatiles of Larix gmelinii

Dendrolimus superans is one of the important pests feeding on the needles of Larix gmelinii. Six standard compounds, (1R)-(−)-α-pinene, (1S)-(−)-α-pinene, ocimene, (1S)-(−)-β-pinene, R(−)-α-phellandrene and camphene, the main volatiles of L. gmelinii were used to test the electroantennogram (EAG) responses of moths. The results show that the order of the EAG responses of moths to seven concentrations of these six compounds were as follows: mated females > virgin females > unmated males, except for 0.1 μL/μL R(−)-α-phellandrene, where the order was: virgin females > mated females > unmated males. There are statistically significant differences between the EAG responses of virgin females and unmated males (p < 0.05), and also between mated females with virgin females and mated females and unmated males (p < 0.01), which suggests that the mated females are more sensitive to the volatiles of host plant. The results of EAG responses of the mated females, virgin females and unmated males indicate that they are more sensitive to R(−)-α-phellandrene than to the other volatile components. The active time for the EAG responses of both mated females and unmated males occurs during the night, i.e., from 20:00 to 04:00 hours. This is consistent with their eclosion, mating and oviposition periods. __________ Translated from Scientia Silvae Sinicae, 2007, 43(7): 55–60 [译自:林业科学]     

寄主树木、寄主和环境因子对松褐天牛深沟茧蜂寄生率的影响研究

[目的]松材线虫病是我国对森林危害和威胁最严重的病害,控制其传播媒介昆虫松褐天牛是防治松材线虫病的主要手段。作者发现的松褐天牛深沟茧蜂(Iphiaulax monochamusi Yang)是寄生松褐天牛中老龄幼虫的重要天敌。为明确松褐天牛深沟茧蜂的寄生率与寄主树木、寄主和环境因子的关系,开展了本研究。[方法]通过解剖46株松褐天牛危害致死的马尾松,调查了松褐天牛深沟茧蜂寄生率与马尾松、松褐天牛和环境因子之间的关系。[结果]调查研究表明:寄主树木的高度、胸径和树龄对松褐天牛深沟茧蜂寄生率没有显著影响,松褐天牛的数量对松褐天牛深沟茧蜂寄生率亦没有显著影响,而松褐天牛幼虫龄期和松褐天牛幼虫在树干上的位置显著影响松褐天牛深沟茧蜂寄生率。松褐天牛深沟茧蜂寄生率与松褐天牛龄期呈显著正相关,其偏好寄生3~5龄幼虫;就天牛在其危害寄主树木上的位置而言,松褐天牛深沟茧蜂偏好寄生马尾松主干上部和在韧皮部危害的松褐天牛幼虫,其对位于马尾松树干上部的寄主幼虫寄生率最高,达27.38%,对在韧皮部生活、危害的寄主幼虫寄生率为20.18%,显著高于位于木质部生活的寄主幼虫寄生率(5.46%)。逐步回归分析表明:影响松褐天牛深沟茧蜂寄生率的关键环境因子是寄主树木的坡位和其它天敌寄生率,其中,坡位与松褐天牛深沟茧蜂呈显著正相关,其它天敌寄生率与松褐天牛深沟茧蜂寄生率呈显著负相关。[结论]以上研究初步明确了松褐天牛深沟茧蜂的寄生率与寄主树木、寄主害虫和天敌之间的关系,为今后利用该重要天敌控制松褐天牛打下了基础。     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.